Bacterial Infections Exam 2 PathoPharm

Staphylococcal Aureus Infections

Symptoms: Skin abscesses, boils, cellulitis, fever, chills, fatigue.

• Physical Signs: Redness, swelling, pus formation at infection site,

tenderness, warmth over affected area.

• Diagnosis: Culture of wound exudate or blood; Gram stain showing

Gram-positive cocci in clusters; PCR for MRSA detection.

• Treatment:

• Drainage if abscess present

• First-line: cephalexin for non-resistant strains

• Severe cases: IV vancomycin, linezolid, or daptomycin.

• MRSA: IV vancomycin or clindamycin.

C.diff infections

Cause → Clostridioides difficile (Gram + anaerobic, spore-forming rod → colonizes GI tract) → fecal-

oral spread of spores → often after antibiotic use → disruption of normal gut flora → toxin

production → pseudomembranous colitis

• Symptoms:

Watery diarrhea → abdominal pain → fever → nausea

• Signs:

• Abdominal distension → tenderness

• Leukocytosis → dehydration

• Diagnosis:

• Stool C. difficile toxin test

• PCR detection of toxin genes

• Colonoscopy → pseudomembranous colitis

• Treatment:

• First-line → oral vancomycin or fidaxomicin

• Severe → vancomycin ± metronidazole

• Discontinue precipitating antibiotics

• Avoid antidiarrheal agents

Clostridium botulinum Infection: Botilism

Gram positive and anerobic, rod shaped and produce spores , found

in soil and foods

• Symptoms: Descending paralysis, difficulty swallowing, blurred

vision, facial drooping.

• Physical Signs: Drooping eyelids, dilated pupils, dry mouth, difficulty

speaking and swallowing.

• Diagnosis: Clinical symptoms, detection of botulinum toxin in

serum, stool, or food.

• Treatment:

• Botulism antitoxin from CDC.

• Supportive care (ventilator support for respiratory failure).

• If wound botulism: Penicillin G or metronidazole.

Clostridium perfringes Infection: Gas Gangrene

Cause → Clostridium perfringens (Gram + anaerobic, spore-forming rod → soil, animal intestines,

human GI tract, raw meats)

• Infection → contaminated traumatic wound → toxin production → rapid tissue necrosis + gas

formation

• Symptoms:

Severe pain → swelling → fever → shock

• Signs:

• Tense swollen skin → discoloration

• Crepitus (gas in tissue) → foul-smelling discharge

• Diagnosis:

• Gram stain → Gram (+) rods

• Wound/blood culture

• Imaging → gas in soft tissue

• Treatment:

• Penicillin G + clindamycin (± doxycycline)

• Urgent surgical debridement

• Hyperbaric oxygen therapy (if available)

Clostridium tetani Infection: Tetanus

Cause → Clostridium tetani (Gram +, anaerobic, spore-forming rod

→ soil/dust/feces)

• Entry → contaminated puncture wounds

• Symptoms:

• Muscle rigidity → painful spasms → lockjaw (trismus)

• Treatment:

• Tetanus immune globulin (TIG)

• Penicillin G ± supportive care

Corynebacterium diphtheriae: Diphtheria

Cause → Corynebacterium diphtheriae (Gram + aerobic rod)

• Infection → throat & mucous membranes → gray pseudomembrane

• Symptoms:

• Sore throat → fever → cervical lymphadenopathy

• Signs:

• Gray tonsillar pseudomembrane → dysphagia → possible airway obstruction

• Treatment:

• Diphtheria antitoxin

• Penicillin or erythromycin

Vibrio cholerae - Cholera

Definition: Infection caused by Vibrio cholerae (Gram −,

anaerobic curved rod) → produces cholera toxin → ↑ intestinal

Cl⁻/water secretion; transmitted via contaminated food/water.

• Symptoms: Profuse watery diarrhea (rice-water stools),

vomiting, severe dehydration.

• Signs: Sunken eyes, dry mouth, hypotension, tachycardia,

oliguria.

• Diagnosis: Stool culture, rapid dipstick test for cholera toxin.

• Treatment:

• Doxycycline (for severe cases).

• Fluid and electrolyte replacement (oral rehydration solutions,

IV fluids for severe cases).

• Zinc supplementation in children.

Bordetella pertussis - Pertussis “Whooping Cough”

Definition: Highly contagious respiratory infection caused

by Bordetella pertussis (Gram − coccobacillus) → paroxysmal

coughing fits followed by inspiratory “whoop”; spread via

respiratory droplets (coughing/sneezing).

• Symptoms: Severe coughing fits, whooping sound on inspiration,

possible vomiting after coughing episodes.

• Signs: Cyanosis, excessive coughing spasms, inspiratory whooping

sound.

• Diagnosis: Nasopharyngeal swab for PCR, culture

• Treatment:

• Macrolides: Azithromycin, clarithromycin, or erythromycin.

• Supportive care (hydration, oxygen if necessary)

Borrelia burgdorferi infection - Lyme Disease

Definition: Lyme disease, caused by Borrelia burgdorferi (gram (-), is a tick-borne illness that can lead to neurological and cardiac complications

Symptoms: Erythema migrans (bullseye rash), fatigue, fever, muscle and joint aches, and swollen lymph nodes

Diagnosis: Clinical presentation, ELISA followed by Western blot, PCR

Treatment: Doxycycline (for adults), amoxicillin (for children), Ceftriaxone for severe cases (e.g., neurologic involvement)

Neisseria meningitidis - Meningitis

Cause → Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae (bacteria infect meninges →

inflammation of brain & spinal cord membranes)

• Transmission → respiratory droplets → colonization of nasopharynx → spread to bloodstream → meninges

• Symptoms:

• Severe headache → fever → neck stiffness → nausea/vomiting

• Signs:

• Positive Kernig’s sign → meningeal irritation

• Positive Brudzinski’s sign → neck flexion → hip/knee flexion

• Photophobia

• Diagnosis:

• Lumbar puncture → CSF: ↑ WBC, ↓ glucose, ↑ protein

• Blood cultures

• PCR pathogen detection

• Treatment:

• Ceftriaxone or cefotaxime

• Vancomycin ± ampicillin (broader coverage)

• Corticosteroids to reduce inflammation

Infections caused by GABHS

Group A beta-hemolytic Streptococcus (GABHS)

causes a variety of infections, which can range

from mild illnesses such as pharyngitis to

severe and life-threatening conditions like

necrotizing fasciitis.

• Secretes virulence factors (exotoxins)

• Streptolysin S and O, streptokinase to

invade the immune system

Strep Pharyngitis

-Caused by GABHS

Cause → Streptococcus pyogenes

Symptoms:

• Sore throat → pain w/ swallowing → fever

Signs (observed):

• Tonsillar erythema ± white exudates

• Cervical lymphadenopathy

Treatment:

• Penicillin or amoxicillin

• Cephalexin → if penicillin allergy

Scarlet Fever

-Caused by GABHS

Cause → Streptococcus pyogenes →

often follows untreated strep throat

Symptoms:

• Fever → sore throat

Signs:

• Diffuse red “sandpaper” rash

• Strawberry tongue

• Pastia’s lines → red streaks in skin folds

Treatment:

• Penicillin or amoxicillin

Impetigo

-Caused by GABHS

Cause → Streptococcus

pyogenes or Staphylococcus aureus

• Highly contagious → common in

children

Symptoms:

• Honey-colored crusted lesions

→ usually around nose or mouth

Signs:

• Vesicles / bullae / pustules →

rupture → ooze → crust

Treatment:

• Topical → mupirocin

• Oral antibiotics → cephalexin,

amoxicillin-clavulanate

Cellulitis

-Caused by GABHS

Cause → Staphylococcus

aureus or Streptococcus pyogenes

• Infection → skin + underlying tissues

(often lower legs)

Symptoms:

• Red, swollen, tender skin → pain → fever

→ chills

Signs:

• Erythema → warmth → edema → possible

abscess

Treatment:

• Antibiotics → cephalexin, clindamycin,

dicloxacillin

• Route → oral or IV depending on severity

Mupirocin

MOA: Inhibits bacterial protein synthesis by binding to

isoleucyl-tRNA synthetase.

• Uses:

• Treatment of skin infections (impetigo, folliculitis)

• Infected wounds (including MRSA)

• ADR: Skin irritation, Allergic reactions

• Rare: systemic absorption leading to more severe side

effects

• Nursing Considerations:

• Apply sparingly to affected area

• Monitor for skin reactions

• Avoid use on large open wounds or broken skin

• Advise patient to wash hands after application

Toxic shock syndrom

-Caused by GABHS

Cause → Staphylococcus aureus or Streptococcus pyogenes (exotoxin superantigens → massive

immune activation) → toxin production from wound, tampon use, surgical site, or skin infection

→ systemic toxin effects

• Symptoms:

High fever → diffuse sunburn-like rash → vomiting → diarrhea → myalgias

• Signs:

• Hypotension → shock

• Desquamation (peeling skin, palms/soles)

• Multi-organ involvement

• Diagnosis:

• Clinical presentation

• Blood or wound cultures

• Treatment:

• IV antibiotics → clindamycin + vancomycin

• Remove infection source

• Supportive care → IV fluids ± vasopressors

Necrotizing Fascititis

-Caused by GABHS

Cause → Group A Streptococcus (Streptococcus pyogenes) or Staphylococcus aureus (toxin

production → rapid soft-tissue necrosis) → infection spreads along fascial planes → severe tissue

destruction

Symptoms: Severe pain → swelling → fever → shock

Signs:

• Rapid tissue necrosis → severe erythema

• Crepitus (gas in tissue)

Diagnosis:

• Clinical presentation

• Imaging (CT/MRI) → fascial involvement ± gas

• Wound/blood cultures

Treatment:

• Urgent surgical debridement

• IV antibiotics → penicillin + clindamycin

• Supportive care → IV fluids ± vasopressors

Post-Streptococcal Glomerulonephritis

-Caused by GABHS

Cause → Group A Streptococcus (Streptococcus pyogenes) infection → immune complex

deposition in glomeruli → inflammation and impaired kidney function

• Symptoms:

Hematuria → edema → hypertension → oliguria

• Signs:

• Facial and peripheral edema

• Elevated blood pressure

• Diagnosis:

• Urinalysis → hematuria, proteinuria

• Elevated ASO or anti-DNase B titers

• ↓ complement (C3)

• Treatment:

• Supportive care

• Antihypertensives

• Diuretics

Rheumatic Heart Disease (RHD)

-Caused by GABHS

Cause → Group A Streptococcus (Streptococcus pyogenes) throat infection → immune cross-

reaction (molecular mimicry) → inflammation of heart valves → chronic valve damage (mitral ±

aortic)

• Symptoms: Fever → joint pain → fatigue → shortness of breath → chest pain

• Signs:

• Erythema marginatum rash

• Migratory arthritis

• Heart murmur → Sydenham chorea (facial tics)

• Diagnosis:

• Elevated WBC, CRP

• Echocardiogram → valve damage

• Throat culture → Group A Streptococcus

• Treatment:

• Penicillin (± long-term prophylaxis)

• Anti-inflammatories → aspirin or corticosteroids

• Valve repair/replacement for severe disease

E.Coli infections

Gram-negative bacillus

• Colonizes normal intestinal flora, especially the colon

• Some strains, like Extended Spectrum Beta-Lactamase (ESBL) producers,

show antibiotic resistance

• Infections Caused by E. coli:

• Urinary Tract Infections (UTIs): A leading cause of both uncomplicated and

complicated UTIs.

• Gastroenteritis: Can cause diarrhea and severe foodborne illness.

• Sepsis and Hemolytic Uremic Syndrome (HUS): Can result from pathogenic

strains like E. coli O157:H7.

Uncomplicated UTIs

Description:

• Occurs in healthy, non-pregnant women → no structural or functional

urinary tract abnormalities

• Symptoms:

• Mild dysuria → urinary frequency → urgency

• Signs:

• Pyuria → bacteriuria → hematuria

• Diagnosis:

• Urine C&S

• Treatment:

• First-line antibiotics → nitrofurantoin (5 days), fosfomycin (single dose),

TMP-SMX (3 days)

• Symptom relief → phenazopyridine for dysuria (urine turns red/orange)

• Follow-up:

• Re-evaluate if symptoms persist → >3 days after treatment

Complicated UTIs

Description:

• Occurs in pts w/ risk factors → male sex, urinary tract abnormalities, diabetes,

immunocompromise, indwelling catheter

• Symptoms: Similar to uncomplicated UTI → more severe → fever/chills, flank pain, N/V

• Signs:

• Fever → pyuria → bacteriuria → hematuria

• CVA tenderness → may progress → sepsis (severe cases)

• Diagnosis:

• Urine C&S

• Ultrasound / CT → if structural abnormality suspected (stones, abscess)

• Treatment:

• First-line antibiotics → ciprofloxacin, levofloxacin, or ceftriaxone

→ IV therapy if severe infection / pyelonephritis

• CAUTI → remove or replace catheter

• Hospitalize if → sepsis, high fever, inability to tolerate PO meds

Streptococcus pheumoniae

Characteristics:

• Gram (+) diplococci → pairs / short chains

• Colonizes → nasopharynx (common in children)

• Resistance:

• DRSP → drug-resistant S. pneumoniae

• PRSP → penicillin-resistant strains

• Additional resistance → macrolides, tetracyclines

• Clinical Significance:

• Leading cause → community-acquired pneumonia (CAP)

• Also causes → otitis media, meningitis

• Severe cases → sepsis (↑ risk in immunocompromised)

Pneumonia Pathogens

CAP – Typical:

• Streptococcus pneumoniae, Haemophilus influenzae

• CAP – Atypical:

• Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella

pneumophila

• HAP / VAP:

• Pseudomonas aeruginosa, Klebsiella

pneumoniae, Staphylococcus aureus (incl. MRSA)

• VAP → same pathogens in mechanically ventilated pts

• Aspiration Pneumonia:

• Anaerobes → Fusobacterium, Peptostreptococcus

Typical Pneumonia

Typical Pneumonia (CAP / HAP / VAP)

(Lobar/Consolidation Pattern)

Physical Signs:

• High fever

• Tachypnea

• Productive cough

• Dullness to percussion (consolidation)

• Localized crackles/rales

•Egophony (“E” → sounds like “A”) over

area of consolidation

• Bronchial breath sounds

• CXR: Lobar consolidation

Atypical CAP

Physical Signs:

• Low-grade fever

• Dry, nonproductive cough

• Minimal chest exam findings

• Normal percussion

• Diffuse or interstitial crackles (if present)

• CXR: patchy/interstitial infiltrates

(not lobar consolidation)

Diagnostics Testing for Pneumonia

Physical Signs:

• Low-grade fever

• Dry, nonproductive cough

• Minimal chest exam findings

• Normal percussion

• Diffuse or interstitial crackles (if present)

• CXR: patchy/interstitial infiltrates

(not lobar consolidation)

Treatment of CAP

Typical CAP

• First-line → high-dose amoxicillin ± doxycycline

• Severe CAP → ceftriaxone + azithromycin or doxycycline

2. Drug-Resistant S. pneumoniae (DRSP)

• Options → high-dose amoxicillin, ceftriaxone, levofloxacin, vancomycin, linezolid

3. Atypical CAP

• Mycoplasma pneumoniae → doxycycline

• Chlamydia pneumoniae → doxycycline

• Legionella pneumophila → levofloxacin

Treatment of HAP/VAP

First-line → piperacillin-tazobactam, meropenem, cefepime (4th gen)

• MRSA coverage → vancomycin or linezolid

• Supportive Care

• O₂ → fluids → analgesics → antipyretics

Pseudomonas aeruginosa infections

Clinical Significance:

• Gram-negative aerobic rod; major

cause of hospital-acquired infections,

especially

in immunocompromised patients.

• Common Sources:

• Ventilator-associated pneumonia (VAP)

• Catheter-associated infections (CAUTI)

• Wounds and burns

• Clinical Signs

• Fever, chills

• Local infection signs → redness,

warmth, swelling, pus

• Characteristic fruity “grape-like” odor

Diagnosis:

• Culture from blood, sputum,

urine, or wound

• Gram stain and PCR identification

• Treatment:

• Non-resistant: Piperacillin-

tazobactam, cefepime,

meropenem

• MDR strains: Ceftazidime-

avibactam, meropenem-

vaborbactam

• Severe infections: Combination

therapy often required